Semiconductor fabrication processes are typically conducted with the substrates supported within a chamber under controlled conditions. For many purposes, semiconductor substrates (e.g., wafers) are heated inside the process chamber. For example, substrates can be heated by direct physical contact with an internally heated wafer holder or “chuck.” “Susceptors” are wafer supports used in systems where the wafer and susceptors absorb heat.
Some of the important controlled conditions for processing include, but are not limited to, fluid flow rate into the chamber, temperature of the reaction chamber, temperature of the fluid flowing into the reaction chamber, and temperature of the fluid throughout the fluid line.
Heating within the reaction chamber can occur in a number of ways, including lamp banks or arrays positioned above the substrate surface for directly heating the susceptor or susceptor heaters/pedestal heaters position below the susceptor. Traditionally, the pedestal style heater extends into the chamber through a bottom wall and the susceptor is mounted on a top surface of the heater. The heater may include a resistive heating element enclosed within the heater to provide conductive heat and increase the susceptor temperature. A major drawback to the resistive pedestal heater is the great deal of heat necessary in order to sufficiently raise the top surface temperature of the susceptor. In order to provide this high level of heat transfer, the pedestal heater and the susceptor interface becomes very hot and may lead to fusion between the two parts. Unfortunately, fusing the susceptor and heater together leads to increased reaction chamber downtime and additional refurbishment/replacement costs. Still further, there remains a continued risk of uneven heating susceptor heating.